Efficiently producing hydrocarbon fluids from downhole formations is a challenging process involving a multitude of different types of equipment and techniques for recovering the fluids from the selected formation. Normally, when production from a hydrocarbon reservoir is commenced, the fluid pressure present in the formation is sufficient to force the liquids to the surface for recovery. After a period of time, however, the natural formation pressure may decline to a point where the pressure is not sufficient to lift the formation fluids to the surface at the desired rate of recovery. In these instances, alternative methods of enhancing the extraction of hydrocarbon fluids from the formation may be employed to augment recovery of formation fluids.
One method of enhancing the recovery of hydrocarbons from a formation is to decrease the hydrostatic head of the column of fluid in the wellbore. Decreasing the hydrostatic head enhances recovery by reducing the amount of pressure required to lift the fluids to the surface. Decreasing the density of the column of fluid extending from the formation to the surface is a technique utilized to reduce the hydrostatic head of the fluid column. For example, mixing a lower density fluid with formation fluids reduces the overall density of the fluid column and consequently decreases the hydrostatic head.
One way to achieve this is by forcing a lift fluid, typically a gas or hydraulic fluid having low density, down the annulus between the production tubing and the casing of the well. The low density fluid is then injected into the production tubing at one or more predetermined locations where it mixes with formation fluids, lowering the density of the fluid column above the formation. The injection of the low density fluid into the production tubing, however, must be carefully controlled to avoid equipment damage while simultaneously providing for optimal recovery. For example, excessive injection rates can result in pressure surges in the tubing and related equipment. Such pressure surges may produce large and destructive forces within the production equipment.
Control of the injection rate is typically accomplished using a metering means such as an orifice, the size of which is typically determined using a trial and error procedure. Thus, the operator attempts to achieve optimum performance of the well by regulating the rate of injection of the lift fluids with various size orifice valves. In practice, the well operator will typically try several orifice settings, allowing the well to stabilize after each adjustment. Due to the distances, location of the valves and the fluid volumes involved, the operator may spend a significant amount of time in making the adjustments, stabilizing production after each adjustment and collecting comparative data from the different settings to establish performance trends.
Therefore, a need has arisen for a lift fluid injection tool that controls the flow of a lift fluid into the production tubing based upon well parameters in an artificial lift well. A need has also arisen for such a tool that does not require the intervention of the well operator to optimize production from the formation. Additionally, a need has arisen for such a tool that periodically monitors and adjusts the injection rate of the lift fluid.